Thin-film transistor array substrate

ABSTRACT

A thin-film transistor array substrate, used in a transflective liquid crystal display. The thin-film transistor array substrate has a substrate, a plurality of pixels, a plurality of scan lines and a plurality of data lines. Each of the pixels has a transparent sub-pixel and a reflective sub-pixel, while the transparent sub-pixel further has a transparent electrode and a first thin-film transistor, and the reflective sub-pixel has a reflective pixel electrode and a second thin-film transistor. The pixel electrode of each sub-pixel is thus electrically connected to a different thin-film transistor. The step of forming a molybdenum layer is thus not required, saving fabrication cost.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of a prior application Ser. No.10/249,991, filed May 26, 2003, now U.S. Pat. No. 7,084,942 which claimsthe priority benefit of Taiwan application serial no. 91114696, filedJul. 03, 2002. All disclosures are incorporated herewith by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates in general to a thin-film transistor arraysubstrate typically used in a transflective liquid crystal display, andmore particularly, to a thin-film transistor array substrate of whichthe pixel electrodes of the transparent sub-pixels and reflectivesub-pixels are electrically connected to different transistors.

2. Related Art of the Invention

The advancement of multimedia basically results from the progress ofsemiconductor device or display apparatus design. Conventional displayapparatus such as the cathode ray tube (CRT) have dominated the marketfor decades due to its excellent display quality and economics. However,issues of space utilization and power consumption exist in cathode raytubes. Therefore, the light, thin, short and small thin-film transistorliquid crystal display (TFT LCD) with high display quality and low powerconsumption has gradually replaced the cathode ray tube to become mainstream in the market. If the fabrication cost of the thin-filmtransistor liquid crystal display can be reduced, the market share andcompetition will be greatly increased. Characterized by the displaymethod, the liquid crystal display can be divided into the transmissivetype liquid crystal display, the reflective type liquid crystal display,and the transreflective type liquid crystal display.

In U.S. Pat. No. 6,195,140, a transreflective type liquid crystaldisplay is described. FIGS. 1 and 2 show the top view and crosssectional view of the conventional transreflective type liquid crystaldisplay. In FIG. 1, a thin-film transistor substrate 100 including athin-film transistor 102 and a pixel 104 is shown. The pixel 104 has areflective region R and a transparent region T. The reflective region Rof the pixel 104 consists of a reflective pixel electrode 106 made ofaluminum material, and the transparent region T of the pixel 104consists of a transparent pixel electrode 108 made of material such asindium tin oxide. Each thin-film transistor 102 is used to control apixel 104 including one reflective pixel electrode 106 and a transparentpixel electrode 108.

FIG. 2 shows the cross sectional view cutting along the line I–II ofFIG. 1. The thin-film transistor 102 has a source/drain region 12electrically connected to the transparent pixel electrode 108. Amolybdenum layer 110 is further formed between the transparent pixelelectrode 108 and the reflective pixel electrode 106. While fabricatingthe pixel 104, formation of the molybdenum layer 110 prevents corrosionproblems caused by electrochemical reaction.

However, in the conventional thin-film transistor array substrate, themolybdenum layer, though improving the corrosion problem caused byelectrochemical reaction, increases the fabrication cost.

SUMMARY OF THE INVENTION

The present invention provides a thin-film transistor array substrateused in transreflective liquid crystal display. Each of the sub-pixelshas a pixel electrode connected to different thin-film transistor tosave the step for forming a molybdenum layer. Therefore, the fabricationcost is reduced.

The thin-film transistor array substrate provided by the presentinvention comprises a substrate, a plurality of pixels, a plurality ofscan lines and a plurality of data lines. Each of the pixels furthercomprises a transparent sub-pixel and a reflective sub-pixel. Thetransparent sub-pixel includes a transparent pixel electrode and a firstthin-film transistor, and the reflective sub-pixel includes a reflectivepixel electrode and a second thin-film transistor.

The first and second thin-film transistors are formed at the same ordifferent sides of the transparent and reflective sub-pixels. When thefirst and second thin-film transistors are formed at the same side, thescan lines are divided into the first scan lines and the second scanlines. The first scan lines are electrically connected to the firstthin-film transistors, and the second scan lines are electricallyconnected to the second thin-film transistors. When the first and secondscan lines are formed at different sides, the first and second thin-filmtransistors are formed at the same scan line or data line andelectrically connected thereto.

BRIEF DESCRIPTION OF THE DRAWINGS

These, as well as other features of the present invention, will becomemore apparent upon reference to the drawings wherein:

FIG. 1 shows the top view of a thin-film transistor array substrate of aconventional transreflective liquid crystal display;

FIG. 2 shows the cross sectional view of the thin-film transistor arraysubstrate as shown in FIG. 1;

FIG. 3 shows the top view of a thin-film transistor array substrate in afirst embodiment of the present invention;

FIG. 4 shows the top view of a thin-film transistor array substrate in asecond embodiment of the present invention; and

FIG. 5 shows the top view of a thin-film transistor array substrate in athird embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 3, in a first embodiment of the present invention, athin-film transistor array substrate 200 of a transreflective liquidcrystal display comprises a substrate (not shown), a plurality of pixels204, a plurality of scan lines 210 and a plurality of data lines 220.Each of the pixels 204 is located between two neighboring scan lines 210and two neighboring data lines 220. Each pixel 204 has a plurality ofsub-pixels.

In this embodiment, each pixel 204 has a transparent sub-pixel 204′ anda reflective sub-pixel 204″. Each transparent sub-pixel 204′ defines atransparent region T, while each reflective sub-pixel 204″ defines areflective region R. Each transparent sub-pixel 204′ includes atransparent pixel electrode 208 and a first thin-film transistor 202 a,while each reflective sub-pixel 204″ has a reflective pixel electrode206 and a second thin-film transistor 202 b. The reflective pixelelectrode 206 is made of a material with high reflectivity such asaluminum, silver, tantalum, tungsten, and alloys of the above. Thesurface of the reflective pixel electrode 206 has a plurality ofprotrusions and recessions to obtain high reflection. The transparentpixel electrode 208 is made of a material with high transmission such asindium tin oxide (ITO). The neighboring transparent and reflectivesub-pixels 204′ and 204″ of the pixels 204 can be formed at the samecolumn or row, or alternately disposed. The present invention does notlimit the position of the transparent and reflective sub-pixels 204′ and204″.

The first and second thin-film transistors 202 a and 202 b are formed atthe same side of the transparent and reflective sub-pixels 204′ and204″, respectively. For example, the first and second thin-filmtransistors 202 a and 202 b are formed at the upper left corner of therespective sub-pixels 204′ and 204″, respectively. The scan line 210 hasat least one first scan line 210′ and at least one second scan line210″. The first and second scan lines 210′ and 210″ are parallel to eachother and extend to the edge of the substrate, so as to electricallyconnect together. In addition, the first thin-film transistor 202 a iselectrically connected to and driven by the first scan line 210′, whilethe second thin-film transistor 202 b is electrically connected to anddriven by the second scan line 210″. That is, the sub-pixel of eachpixel 204 such as the transparent sub-pixel 204′ and the reflectivesub-pixel 204″ are disposed at two neighboring data lines 220 betweenthe first scan line 210′ and the second scan line 210″. The first scanline 210′ and the second scan line 210″ can belong to the same scan lineor the neighboring scan lines.

Thereby, each transparent or reflective sub-pixel are separatelydisposed and driven by different thin-film transistors without formingthe additional molybdenum layer. The corrosion problem caused byelectrochemical reaction is thus resolved.

FIG. 4 shows a top view of a thin-film transistor array substrate 300 ofa transreflective liquid crystal display in a second embodiment of thepresent invention. The thin-film transistor array substrate 300comprises a substrate (not shown), a plurality of pixels 304, aplurality of scan lines 310 and a plurality of data lines 320. Thepixels 304 are located on the substrate between two neighboring datalines 320. Each of the pixels 304 has a transparent sub-pixel 304′ and areflective sub-pixel 304″. The transparent sub-pixel 304′ defines atransparent region T, while the reflective sub-pixel 304″ defines areflective region R. The transparent sub-pixel 304′ comprises atransparent pixel electrode 308 and a first thin-film transistor 302 a,and the reflective sub-pixel 304″ comprises a reflective pixel electrode306 and a second thin-film transistor 302 b.

In this embodiment, the first thin-film transistors 302 a and the secondthin-film transistors 302 b are disposed at opposing sides of thetransparent sub-pixel 304′ and the reflective sub-pixel 304″,respectively. That is, the first thin-film transistor 302 a of thetransparent sub-pixel 304′ and the second thin-film transistor 302 b ofthe reflective sub-pixel 304″ of the same pixel 304 are disposed at twosides of the scan line 310 and are electrically connected thereto.Therefore, the same scan line 310 drives the first and second thin-filmtransistors 302 a and 302 b simultaneously.

FIG. 5 shows a top view of a thin-film transistor array substrate 400 ofa transreflective liquid crystal display in a third embodiment of thepresent invention. The thin-film transistor array substrate 400comprises a substrate (not shown), a plurality of pixels 404, aplurality of scan lines 410 and a plurality of data lines 420. Thepixels 404 are located on the substrate between two neighboring datalines 420. Each of the pixels 404 has a transparent sub-pixel 404′ and areflective sub-pixel 404″. The transparent sub-pixels 404′ define atransparent region T, while the reflective sub-pixels 404″ define areflective region R. Each transparent sub-pixel 404′ comprises atransparent pixel electrode 408 and a first thin-film transistor 402 a,and each reflective sub-pixel 404″ comprises a reflective pixelelectrode 406 and a second thin-film transistor 402 b.

In this embodiment, the first thin-film transistors 402 a and the secondthin-film transistors 402 b are disposed at different sides of thetransparent sub-pixel 404′ and the reflective sub-pixel 404″,respectively, but are electrically connected to the same data line 420.That is, the first thin-film transistor 402 a of the transparentsub-pixel 404′ and the second thin-film transistor 402 b of thereflective sub-pixel 404″ of the same pixel 404 are disposed at twosides of the data line 420 and are electrically connected thereto.

Referring to FIGS. 3 and 5, it is appreciated by people of ordinaryskill in the art that when the pixels are disposed on the substrate attwo neighboring scan lines and the first and second thin-filmtransistors of the transparent and reflective sub-pixels of the pixelare located at the same side, the data line may include a first dataline and a second data line parallel to each other to extend to andbeing electrically connected at the edge of the substrate. The firstthin-film transistor is electrically connected to and driven by thefirst data line. The second thin-film transistor is electricallyconnected to and driven by the second data line. FIG. 3 shows the firstscan line 210′ and the second scan line 210″ formed by similar design.

In the present invention, the transparent region T and the reflectiveregion R of the transreflective pixel have various kinds of allocationswith various driving mechanisms. The ratio of the transparent region Tto the reflective region R is about 1:1, for example. It is appreciatedthat the display area of the transparent region T and the reflectiveregion R can be adjusted other than 1:1 according to specific displayrequirement without exceeding the scope of the present invention. Inaddition, the allocation of the above transparent region T and thereflective region R can be used in the same array substrate to optimizethe display quality.

According to the above, the present invention has at least the followingadvantages.

1. The reflective and transparent sub-pixels of the thin-film transistorarray substrate of the transreflective liquid crystal display areelectrically connected to different thin-film transistors, such that themolybdenum layer formed between the transparent and reflectivesub-pixels is not required. The process for forming the transreflectiveliquid crystal display is thus simplified.

2. The location of the thin-film transistor for each sub-pixel of thethin-film transistor array substrate of the transreflective liquidcrystal can be adjusted according to the process or product requirement.

Other embodiments of the invention will appear to those skilled in theart from consideration of the specification and practice of theinvention disclosed herein. It is intended that the specification andexamples be considered as exemplary only, with a true scope and spiritof the invention being indicated by the following claims.

1. A thin-film transistor array substrate applied to a transflectiveliquid crystal display, comprising: a substrate; a plurality of scanlines on the substrate, wherein each of the scan lines further comprisesa first scan line and a second scan line extending therefrom, and thefirst scan line is electrically connected to the second scan line; aplurality of data lines on the substrate; a plurality of transparentsub-pixels on the substrate, wherein each of the transparent sub-pixelscomprises a transparent pixel electrode and a first thin-filmtransistor, and the first thin-film transistor is electrically connectedto the first scan line; and a plurality of reflective sub-pixels on thesubstrate, wherein each of the reflective sub-pixels comprises areflective pixel electrode and a second thin-film transistor, and thesecond thin-film transistor is electrically connected to the second scanline.
 2. The thin-film transistor array substrate according to claim 1,wherein the first scan line and the second scan line are parallel toeach other and extend to an edge of the substrate.